The present invention relates to a lining tube for use in repairing an existing pipeline, particularly to a lining tube reversible into an existing underground pipeline such as a gas pipe, water pipe, etc. so that its initial inner surface becomes outer surface which adheres to the internal surface of the existing pipeline.
FIG. 7 shows a process where a reversible lining tube 6 is reversed into an existing underground pipeline 1 to repair the same, which process has been disclosed in Japanese Patent Application No. 7-229165.
According to the process shown in FIG. 7, at first, a resilient leading pig 3 is introduced into the existing underground pipeline 1. Then, a necessary amount of adhesive agent 5 is introduced into the pipeline 1. Afterwards, one end of a reversible lining tube 6 is fixed at an open end 1a of the pipeline 1 in a manner such that the lining tube 6 may be reversed into the pipeline 1.
As shown in FIG. 7, a suction apparatus P is connected to an opposite open end 1b of the pipeline 1, so that a negative pressure may be produced into the pipeline 1 to cause the leading pig 3 and the adhesive agent 5 to move towards the open end 1b of the pipeline 1, thereby enabling the reversible lining tube 6 to be reversed into the pipeline 1. In this way, the initial inner surface of the lining tube 6 becomes outer surface which adheres to the internal surface of the existing underground pipeline 1.
Alternatively, instead of using a suction apparatus P, it is possible to connect a pressurizer apparatus (not shown) to the open end 1a. Then, by operating the pressurizer apparatus, a positive pressure is produced into the pipeline 1 to cause the leading pig 3 and the adhesive agent 5 to move towards the open end 1b of the pipeline 1, thereby enabling the reversible lining tube 6 to be reversed into the pipeline 1. In this way, the initial inner surface of the lining tube 6 becomes outer surface which adheres to the internal surface of the pipeline 1.
The lining tube 6 used in the process shown in FIG. 7 comprises an elastomer layer 10 (for instance, polyurethane layer) and a fabric layer 11 (consisting of laterally arranged threads and longitudinally arranged threads), as illustrated in FIG. 8.
Referring again to FIG. 8a-8b, when the lining tube 6 comprising the elastomer layer 10 and the fabric layer 11 is reversed into the pipeline 1, the fabric layer 11 becomes an outer layer to absorb the adhesive agent 5 so as to adhere to the internal surface of the pipeline 1.
However, since the fabric layer 11 has a considerable thickness and a hardness, it is difficult to reduce the overall thickness and hardness of the lining tube 6. As result, when the lining tube 6 is reversed in the pipeline 1, it has been found that the reversal of the lining tube 6 in the pipeline 1 is relatively difficult, especially when passing through a bent portion 1c of the pipeline 1.
On the other hand, as illustrated in FIGS. 9a-9b, if a lining tube consisting only of a single layer 10 (elastomer layer) is used in repairing an existing underground pipeline 1, it is found that the reversal of the lining tube in the pipeline 1 is easier than the lining tube shown in FIGS. 8a-8b, especially when passing through a bent portion 1c of the pipeline 1.
However, since the elastomer layer 10 fails to absorb the adhesive agent 5, it has been found that the lining tube shown in FIGS. 9a-9b is difficult to adhere to the internal surface of the pipeline 1. Also, since the elastomer layer 10 fails to absorb the adhesive agent 5, an adhesive agent layer 5 formed between the elastomer layer 10 and the pipeline internal wall will become uneven, causing an uneven surface of the lining layer on the pipeline internal wall.